In wireless body area network (WBAN), the WBAN sensors usually transmit encrypted data for the sake of security. But because of this, finding and getting the required data quickly becomes a challenge. Thus, many scholars have proposed searchable encryption (SE) schemes. Regrettably, many proposed SE schemes are not resistant to inside keyword guessing attack (IKGA), and most schemes are not suited for cross-domain communication in WBAN because they use single cryptosystem and the same cryptographic system parameters. To address the aforementioned issues, we put forward a new SE scheme for WBAN based on the public key cryptosystem in this paper. Our scheme allows WBAN sensors in certificateless public key cryptography (CLC) and receivers in public key infrastructure (PKI) environment use different cryptographic system parameters to realize cross-domain heterogeneous communication. At the same time, our scheme can effectively resist IKGA. Compared to the five existing schemes, the total computation cost of our scheme reduced by at least 59.99%.